#100: Portrait of a Violent Star

This ultraviolet image of the sun was captured by the NASA Solar Dynamics Observatory (SDO), launched last February to monitor Earth’s temperamental star with unprecedented precision. The purplish aura reveals high-arcing loops of 3.6-million-degree plasma that link sunspots and other magnetic areas on the surface; white lines illustrate computer calculations of how the magnetic areas connect. Occasionally eruptions on the sun are so powerful that they can cripple Earth’s electrical grids and global positioning satellites. SDO’s observations will help scientists understand the mechanism behind these outbursts—research that is particularly important as the sun awakens from its longest slumber in a century (see “Plasma Rivers Explain the Quiet Sun”).